Re: Mixed L2R and R2L paragraphs and horizontal scroll

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 30 Jan 2010 20:45:50 +0100
> From: martin rudalics <rudalics@gmx.at>
> Cc: emacs-bidi@gnu.org, emacs-devel@gnu.org
> 
>  >> Inconvenient for the user.  Why scroll something out of view if there's
>  >> no urgent need to do so.  (Although a similar argument could be made for
>  >> pure LR text as well
>  >
>  > Exactly!  So perhaps we should adopt this design,
> 
> Which one?

The one that scrolls the R2L lines to the right when the L2R lines are
scrolled to the left.

>  >>  > That's what would happen if the second line was
>  >>  > displayed at the left margin, like this:
>  >>  >
>  >>  >       +---------+---------+-------------------+
>  >>  >       |$ijk     |abcdefgh$|abcdefghijk        |
>  >>  >       |$IJK     |$HGFEDCBA|        KJIHGFEDCBA|
>  >>           ^^^^^^^^^
>  >>  >       |         |         |                   |
>  >>  >       +---------+---------+-------------------+
>  >>
>  >> I fail to understand the marked text in your example.
>  >
>  > In the current unidirectional display, where text is always displayed
>  > in its logical (i.e. reading) order, the second line would have been
>  > displayed as "ABCDEFGHIJK", flushed to the left margin.  Then when the
>  > line above it is scrolled to show just "$ijk", so would be the second
>  > line, and it would display as "$IJK".
> 
> I still don't get you.  In your earlier examples capitalized text always
> showed reverse as KJI and not as IJK.

Yes, and they were also flushed to the right.  This is what the
bidirectional display does.  In the above example, the leftmost window
is displayed as with the current unidirectional display engine we have
in Emacs 23.  That is why it is flushed to the left and the R2L text
is not reversed.

> But I also fail to understand why
> there's no text on the right of this.  So maybe you meant something like
> 
>        +---------+---------+-------------------+
>        |$ijk     |abcdefgh$|abcdefghijk        |
>        | KJIHGFE$|        $|        KJIHGFEDCBA|
>        |         |         |                   |
>        +---------+---------+-------------------+
> 
> (no text in the second line of the second window) instead?

No, I meant what I wrote.  The middle window was not scrolled, and
there's no need to change anything in it just because the leftmost
window was scrolled.